The present invention relates in general to plastic plugs and closures which are removeable from their corresponding container by means of an integral pull ring. More specifically, the present invention relates to the design of a molded plastic plug for use with five-gallon (20 liter) containers which contain a paint product.
Five-gallon (20 liter) containers are typically used for non-tinted base paint products. These containers have an outlet opening which is closed by a suitable tint plug. When the painter acquires the initially filled container, the tint plug is removed and a paint tint is added. The tint plug is reinstalled, the paint constituents in the container are mixed, and the container is then transported to the job site. Typically these five-gallon paint containers (pails) are used by professional painters where the entire container with the lid removed adapts to their automatic paint application equipment.
Some of the problems with existing tint plug designs are that the plugs do not stay securely in the outlet opening when they are supposed to or the plugs are difficult to remove. There needs to be a balance which must be established between a tight fit for leak-proof handling and easy removal for the convenience of the user. The plug must remain secured in the outlet opening and establish a leak-proof seal during normal shipping and handling. The user, who may be unskilled, needs to be able to easily remove the tint plug without splashing paint which will be on the inside surface of the tint plug. Additionally, the tint plug must be easily reinstalled and effect a seal for transport between the tinting location and the job site.
The market for tint plugs is quite competitive and price is of utmost importance. In order to remain price competitive, tint plugs are typically molded from relatively inexpensive thermoplastic materials. The price constraints also limit the number of design options and features which can be incorporated into the tint plug.
In addition to those plug and closure designs described by the various patent references listed hereinafter, there are two current designs which are deserving of additional discussion. One design has a pull-ring connected to the bottommost horizontal surface of the cap. This design is intended to reduce the extraction force by collapsing the sidewall. As the horizontal surface is forced upwardly, its circumference tends to pull at the sidewall effectively trying to turn the basic cup-shaped configuration inside out. This is intended to reduce the diameter of the retention bead (a small circumferential ridge on the closure engaging the bottommost edge of the container opening) allowing the closure to be easily removed. It is believed that in actual practice, this particular concept does not work very well.
Another design which is appropriate of specific mention incorporates a pull ring which is attached to the inside of a vertical wall portion of the closure. The intent with this design is to collapse the sidewall in order to disengage the retention bead in one localized area. The next step with this particular design is for the closure to be "walked" or "rocked" off of the opening. While this concept may appear to be functional, the juncture of the pull ring and the sidewall forms a localized thick point. Special manufacturing precautions must therefore be made in order to ensure that this variation in wall thickness does not cause what is typically known as a "sink". A sink in the sidewall of the tint plug would be a leak path for the package lading.
The subject invention solves both problems inherent with these two existing designs. In the present invention the pull ring is molded to the bottommost portion (closing diaphragm) keeping the sidewall of uniform thickness, and thereby eliminating any sinks. The closing diaphragm has an inclined portion which angles upwardly as it extends outwardly. The pull ring is molded to this inclined surface at a location adjacent to the sidewall. This particular style of molded assembly enables a localized pressure to be exerted on the retention bead. The purpose is to deform the retention bead inwardly and rock the bead out through the container outlet opening. Once the retention bead is initially pulled away from the container outlet opening, the force required to rock the remainder of the bead is minimal. The critical area is the initial retention bead release from the outlet opening. As indicated, the angled portion of the closing diaphragm localizes the pull ring forces with respect to the retention bead. To further define and reduce the area where the retention bead initially releases from the outlet opening, it is desirable for the sidewall to deform or collapse in a controlled manner. In order to achieve this function, three inverted, generally V-shaped notches are provided in a lower rib portion of the sidewall. These three notches relieve the hoop strength which is inherent in the cylindrical sidewall design and contributes to an easier release of the retention bead from the outlet opening.
The present invention provides a tint plug which requires less force for removal while at the same time providing an enhancement to those portions of the design which prevent leaks. The present invention allows the retention bead to be made larger with respect to the sealing surface which is defined as the area between the retention bead and the bottom of the upper annular flange. This in turn improves the performance of the tint plug of the present invention during shipping and handling of the container.
In addition to the two designs described above, there are a variety of plastic plug and closure designs which have been patented over the years. Some of these patented designs include a pull tab or pull ring, while other designs incorporate features which are specifically styled for a particular need or problem. The following listed patents are believed to provide a representative sampling of these earlier patented plugs and closures:
______________________________________ PATENT NO. PATENTEE ISSUE DATE ______________________________________ 5,271,519 Adams et al. Dec. 21, 1993 4,747,511 Dutt et al. May 31, 1988 4,712,707 Pavely Dec. 15, 1987 4,738,376 Markus Apr. 19, 1988 4,431,110 Roth Feb. 14, 1984 3,080,088 Corrinet Mar. 5, 1963 3,200,986 Grutta Aug. 17, 1965 4,706,838 Von Holdt Nov. 17, 1987 4,442,949 Dwinell et al. Apr. 17, 1984 4,328,906 Walter May 11, 1982 3,248,002 Song Apr. 26, 1966 Des. 248,453 Summers Jul. 11, 1978 Des. 263,799 Nilsson Apr. 13, 1982 ______________________________________
Notwithstanding the variety of designs and concepts set forth in these various listed patents, the present invention is believed to be novel and unobvious in several respects.